Some integrated circuit devices such as microprocessors or microcontroller units (MCUs) require signals which provide bidirectional information, such as handshaking, between one or more such devices which may be present in a system. These signals are output signals to the device at certain points in time, and subsequently become input signals. The output buffers providing these input/output signals are also typically open drain. Open drain output buffers allow multiple devices in a system to be connected in a wire-OR fashion. The output driver is typically an N-channel MOS transistor whose drain provides the output signal and whose source is connected to a negative power supply voltage terminal V.sub.ss, approximately 0 volts.
A problem arises with such an input/output circuit in certain applications, especially MCU applications. When an MCU drives and then negates the signal, the voltage of the wire-OR signal must rise to an appropriate level before it is sampled by the MCU. In order to minimize power consumption, a large-valued pullup resistor may be used. However the large-valued resistor makes an associate RC time constant large, and when the MCU samples the signal it may still be seen as a logic low. On the other hand, some applications where speed is critical require the signal to be sampled quickly and can tolerated smaller-valued resistors in order to pull up the signal faster. When to sample the signal as an input thus presents comflicts between different applications.